Reproductive Ability in relation to boar taint risk in entire male pigs – AROME

Public pressure to abandon castration has led stakeholders within the European Union to sign a voluntary declaration to end pig chirurgical castration practices by January 2018. Abandoning surgical castration will be beneficial:
- for animal welfare with the reduction of pain,
- for pig breeders as castration is an unpleasant task and non castrated male pigs are more feed efficient, grow faster and are leaner than castrates resulting in improved farmer’s income
- for the environment as entire male pigs excrete less nitrogen and phosphorus and have a lower contribution to global warming due to better feed efficiency.
Then, this change in pig breeding practice could largely improve environmental, social and economic performance but is not without adverse consequences on meat quality. Respecting pig welfare without affecting product quality can be a delicate compromise as perfectly illustrated by boar taint issue.
Boar taint is an offensive perspiration-like and urine-like unpleasant odour and flavour released when heating meat. It has been known for decades that boar taint is directly related to sexual development and this is one of the very first reasons for castrating young male pigs. The proportion of tainted carcasses depends on many factors, including genetics. The selection of lines with a low risk of developing boar taint is now considered the most desirable solution in the medium to long term in order to avoid all kind of castration, both surgical and immunological. Though it has been evidenced that selection against boar taint is feasible, it has never been properly settled in pig populations for two main reasons. Firstly, up to now, boar taint issue was perfectly overcome by castration and boar taint is still difficult and expensive to measure though some alternative measurements are under study. Secondly, considering the close relationship between boar taint and steroid production, a “crude” selection against boar taint is likely to impair reproductive ability of males and females. Thus, with the ban of male pig castration expected within the next few years, the challenge will be to perform an efficient selection against boar taint, without degrading reproductive traits especially without increasing the proportion of animals with reproductive failures.
Currently, the only reliable way to measure boar taint is to collect a fat sample, either by biopsy on live animals or on carcass of slaughtered animals. The reference method is a long and expensive dosage of androstenone and skatole. The human nose method is an option for sorting carcasses at slaughterhouse but results are not highly reliable and the method has not yet been proven to be efficient for breeding programs. In all cases, the sexual maturity status at slaughter is unknown: the animal can be from prepubertal (with no risk of boar taint) to fully mature. It is thus impossible to differentiate animals with delayed puberty from animals with a true low potential for boar taint compound accumulation, even after sexual maturity. As a consequence, we need to develop knowledge, methods and tools to be widely implemented in breeding programs for identification of animals with low boar taint but good subsequent reproductive ability and promote an efficient selection procedure. That is the key point to carry out a selection against boar taint without affecting reproductive ability.
Improving animal welfare and lowering the environmental impact of pig production, without impairing long term economic viability of pig production because of deteriorated meat quality and reproductive performances is a real strategic challenge for breeding companies at an international level. To settle this difficult compromise, it is essential, as it is aimed in the AROME project, to acquire additional knowledge on relationships between boar taint risk and reproductive traits both at individual and population levels.